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@PHDTHESIS{Zhang:809232,
      author       = {Zhang, Yanli},
      title        = {{D}evelopment of {E}mbedded {T}hermocouple {S}ensors for
                      {T}hermal {B}arrier {C}oatings ({TBC}s) by a {L}aser
                      {C}ladding {P}rocess},
      volume       = {312},
      school       = {Ruhr-Universität Bochum},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2016-02521},
      isbn         = {978-3-95806-129-3},
      series       = {Schriften des Forschungszentrums Jülich Reihe Energie $\&$
                      Umwelt / Energy $\&$ Environment},
      pages        = {II, 108 S.},
      year         = {2016},
      note         = {Ruhr-Universität Bochum, Diss., 2015},
      abstract     = {Thermal barrier coatings (TBCs) are now being widely used
                      on gas turbine engines to lower the surface temperatures of
                      metallic substrate from extreme hot gas stream in combustor
                      and turbine components. The thermally grown oxide (TGO)
                      growth rate plays an important role in the lifetime of TBC
                      systems. The accurate real-time monitoring of bond-coat/
                      8YSZ interface temperature in thermal barrier coatings
                      (TBCs) in hostile environments opens large benefits to
                      efficient and safe operation of gas turbines. A new method
                      for fabricating high temperature thermocouple sensors which
                      can be placed close to this interface using laser cladding
                      technology has been developed. K-type thermocouple powders
                      consisting of alumel (Ni2Al2Mn1Si) and chromel (Ni10Cr) were
                      studied as candidate feedstock materials. A thermocouple
                      sensor using these materials was first produced by coaxial
                      continuous wave (CW) or pulsed laser cladding process onto
                      the standard yttria partially stabilized zirconia (7~8
                      $wt.\%$ YSZ) coated substrate and afterwards embedded with a
                      second YSZ layer deposited by the atmospheric plasma spray
                      (APS) process. The process parameters of the laser cladding
                      were optimized with respect to the degradation of the
                      substrate, dimensions, topography, thermosensitivity and
                      embeddability, respectively. Infrared cameras were used to
                      monitor the surface temperature of clads during this
                      process. The manufacture of the cladded thermocouple sensors
                      provides minimal intrusive features to the substrate. The
                      dimensions were in the range of two hundred microns in
                      thickness and width for CW laser cladding and less than 100
                      microns for pulsed laser cladding. Additionally, continuous
                      thermocouple sensors with reliable performance were
                      produced. It is possible to embed sensors manufactured by CW
                      laser cladding rather than by pulsed laser cladding due to
                      the limited bonding strength between the clads and the
                      substrate. Periodically droplets were formed along the clads
                      under improper parameters, the mechanism to this is
                      discussed in terms of particle size distribution after
                      interaction with the laser beam, melts duration and
                      Rayleigh’s theory. To sum up, laser cladding is a
                      prospective technology for manufacturing microsensors on the
                      surface of or even embedded into functional coatings that
                      can survive in operation environments for in-situ
                      monitoring. Production of sensors within thermal barrier
                      coatings (TBCs) increases the application field of the laser
                      cladding technique.},
      cin          = {IEK-1},
      cid          = {I:(DE-Juel1)IEK-1-20101013},
      pnm          = {113 - Methods and Concepts for Material Development
                      (POF3-113) / HITEC - Helmholtz Interdisciplinary Doctoral
                      Training in Energy and Climate Research (HITEC)
                      (HITEC-20170406)},
      pid          = {G:(DE-HGF)POF3-113 / G:(DE-Juel1)HITEC-20170406},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/809232},
}